Ballpointed writing instruments



Sept. 19, 1961 H. R. FEHLING 3,000,090

BALLPOTNTED WRITING INSTRUMENTS Filed Aug. 25, 1958 11n/U 6125501* H. fi, Fel?, L L17/y United States Patent() 3,000,090' BALLPOINTED WRITING INSTRUNIENTS Hans Reinhard Fehling, Zug, Switzerland, assignor to LRC. Limited, London, England, a company of Great Britain Filed Aug. 25, 1958, Ser. No. 756,909' p g Claims priority, application Great Britain Aug. 28, 1957 5 Claims. (Cl, 29-441) is invention relates to Writing' instruments ofi the ballpo'inted type in which the Writing extremity or nib comprises a writing ball rotatably' mounted in andY partly protruding from a socket or housing, which ball may' be supplied with ink from a reservoir by' means of an' inl; feed duct which connects with the rear of the socket or' housing so that, as the ball is rotated in its socket or housing by being moved over and in Contact: with a. surface such as, for example, that of' a sheet. of paper, a thin lilm of ink will be carried by the'vball through the narrow' gap between it and its housing and deposited as a trace on the said surface.

ln writing instruments of this type, partlspheri'cal. ball se'atings in the interior of the housing which are essential for a satisfactory writing performance can only beformed accurately by producing impressions of the writing ball` itself on, the bottom of the socket and on the housing wall. This is' usually accomplished when the housing with a writing ball positioned therein is' subjected to a peeping, swaging, pressing or other suitable' operation to' c'onstrict the lip of the ball housing and retainz the ball in' position. When in such an operationl a' sunic'ie'n't. force' is applied to press the housing walls on to the ball surface the interior surfaces of the housing'V in contact' with the ball" retain the shape of the latter by permanent deforma1 tion. This operation may beV preceded by' impressing 'the ball on the bottom of the housing. It will be appreciatedV therefore that in this method of forming suitable spherical ball seatings, the only clearance between the ball and the seatings through which the ink will be carried during writing, is' that produced as `a result of the elasticrecovery' of the metal after release of the external pressure applied during the ball retaining' operation.- This method has' been found reasonably satisfactory with metals such as brass or aluminum alloy which dueto a' high yield stress show a signicaut degree of elastic recovery, but less' so' with'l the metals at present suitable for die-,casting such as,- for example, tin alloy, since these have a low' elastic limit and do not recover sutliciently' after' the operation to retain the' ball in position to afford an adequate clear.-Y ance between ball and seating; v It is an object of the present invention. therefore to' provide a method by which the clearance between the writing ball and its' spherical seatings in the housing of. a nib,- and particularly ar die-cast' nib, may be conveniently and accurately' increased.

It is known that the effective clearance of a nib made ofA brass' or similar material can be increased by exterior rolling or spinning (after the conventionalV ball retaining operation) that part of the housing walls which form the lateral seatfor the 'balk It is believed that the opera tion results in a lengthening of the perimeter of the thin annular section forming these walls thus increasing the clearance. The method is. lghly sensitive to' very small changes of working conditions, and the range of increase in clearance is very limited. It can only be applied on nibs having very' thin housing walls. Moreover,` for reasons which are not fully understood this method does not produce any signicant increase in ball clearance when applied to nibs made in tin alloy or similar metals having `a low yield stress. Alternatively, when too much force is applied the operation results in distortion of the Paf'ented Sept. 19, 1961 housing walls which leads to a very unsatisfactory writ ing performance.

The present. invention consists of, in the manufacture of a ballpointed writing. instrument of the type described, the method ofV increasing the clearance between the writ-i ing ball `and its seatings in the housing by subjecting the exterior ofi the nib to' aconstricting force or forces in a zone extending circumferentially of the nib exterior and located to the rear of the plane tangential to the rear of the ball and perpendicular to the axis ofthe nib housing.

lutheaccompanying drawings:

FIGURE 1 showsin section one arrangement for carrying outV the method according to the present invention, and

FIGURE 2 shows a modified arrangement.

Inv carrying the invention into eliect according to one convenient mode by way of example as shown in FIG- URE l, a die 1, having `a bore 2, isV placed on the nib 3 so that the peripheral edge of the bore 2, whichV is chamfered at 4, contacts the tapering exterior of the nib along a circumferentially extending zone in the form of. a circular band 5 in a` plane to the rear of the plane X-X tangential to the rear of the ball. 6 and perpendicular to the axis of the nib 3. The die 1, is then impacted or4 pressed onto the nib 3 with aY force suicient to increase the clearance between the ball 6 and its spherical seat' ings 7 and 8 to the desired: size. Alternatively, but. not shown, the peripheral. edge. ofthe bore need not be chamferedA in which. case the exterior of the nib 3 will be contacted.V along a circular line instead of along the band 5..

,As far as can be. ascertained the operation results in. slightly constricting the transverse section of the nibv the plane of impact and, as a reaction, `in a slight expan-V sion of the housing walls as a whole, thus producing a generally increased clearance Ibetween the ball andA the housing walls.

The modifiedr arrangement4 shown. in FIGURE 2 is preferably employedv on a nib 3 whose exterior has atapering portion 3a in. frontV of a cylindrical portion 3b of small diameter. In this case the `die 1 conveniently has a. tapering bore 9 e.g. of 40 degrees included angle, which engages the edge 1.0 between the tape-ring 3a eg.. ofY 50 degrees, andcylind'ricall 3b portions along a circularr line and when. faced towards the nib 3 causes a rearward displacement of the edge 10 and consequent local reduction. of the con-icalangle of the nib 3 with the desired increase of. the clearance between the ball 6 and' its seatings. It will be appreciated that in many cases the edge 10 will. not be clearly defined and will rather take the form of a. convex region between the tapering 3a and, cylindrical 3b portions.Y

It hasy been found. that. the most critical factor in the method according to the present invention is the position of the plane transverse to the axis of the nib in front of which the metal is free to move, i.e., the plane at, and possibly also behind which, the constrictive forces are caused to act on the nib. For example, in the methods as setV forth. above the'. optimum location ofv this plane is determined by the diameter ofy the bore. If the' plane is too far forward, ie., in front of or in the planeJ tangential to the rear. of. theball transverse to the axis of. the nib, the process either does not produce any signicant increase in. gap4 size or produces nibs having unsatisfactory or varying Writingy performance. lf the plane isV too backward, then either no increase in clearance is produced or too` large a force is required to produce a satisfactory clearance. For nibs of conventional shape, e.g. according to FIGS. l and 2, it has been found that the best location for the plane in which the main constrictive eiect takes place is 0.85 to 0.95 mm. to the rear of the ball centre n the case of -a ball of 1 mm. in diameter. It is in most cases advisable to move the plane further backwards if the nib diameter is smaller, i.e. the walls surrounding the ball and the feed duct are of thinner section.

' One advantage of this method is its great simplicity and the ease and precision with which it can be repeated in continuous mass production. A further advantage is 'the wide range of increase in ball clearance which can be obtained by this method without any deleterious effects on the writing performance.

It will be appreciated that in order to obtain satisfactory results it is important to have a nib which, at least in front of the plane of contact, is completely symmetrical, i.e., such that the metal forming the housing walls is symmetrically disposed about the longitudinal axis of the nib thus fo-rming a housing Wall having constant circumferential thickness in any particular plane transverse to the axis of the nib.

It is equally important that the constricting tool should be made and maintained to such a standard of symmetry and accuracy that the impression made by it on the exteriorrof the nib is symmetrically disposed about said axis, perpendicular to the latter and of uniform depth. It will be appreciated by those skilled in the art that there should be the best possible `alignment between the axes of the nib and of the constricting tool prior to applying the constricting force. Foi` this reason, such shapes of the constricting tool are preferred which provide for self-alignment when placed on the nib, as in FIGS. l and 2.

' Any other suitable method may be used to apply the constricting force to the exterior of the nib such as, for example, rolling or swaging. However, constricting by impact is preferred because it greatly simplifies the problem of keeping rthe constrictive elort constant in mass production on fully automatic machines, eg. of the turntable type known in the art. I It is preferred to carry out the operations of retaining the ball in position and of carrying out the method of increasing the clearance according -to the present invention in one setting.

If desired, the method according to the present invention can be carried out in more than one stage. But in general this will not be necessary.

I claim:

1. In the manufacture of a ballpointed writing instrument having a nib comprising a metal ball-accommodating housing including lateral ball seatings in the wall of the housing of substantially constant circumferential thickness and a metal ball mounted therein, the method of increasing the clearance between'the Writing ball and its seatings in the housing which consists in subjecting the exterior of the nib to a constricting force exceeding the elastic limit of the nib structure in a Zone which extends eircumferentially around the nib exterior tov assure a permanent deformation of the nib, which zone is located parallel to and to the rear of the plane tangential to the rear of the ball and perpendicular to the axis of the nib and no greater than three ball diameters radially distant from the center of the writing ball, such that the nib is deformed to increase the clearance between the Writing ball and its seatings in the nib housing.

. 2. In the manufacture of a ballpointed writing instru` ment having a nib comprising a metal ball-accommodating housing including lateral ball seatings in the wall of the housing of substantially constant circumferential thickseatings in the housing which consists in forcing a tool having a bore onto the exterior of the nib such that the end of the bore contacts and applied a constricting .4 force exceeding the elastic limit of the nib structure to a zone which extends circumferentially of the nib exterior to assure a permanent deformation of the nib, which zone is located parallel to and to the rear of the plane tangential to the rear of the ball and perpendicular to the axis of the nib and no greater than three ball diameters radially distant from the center of the writing ball, such that the said clearance is increased.

3. In the manufacture of a ballpointed Writing instrument having a nib comprising a metal ball-accommodating housing whose exterior has at least a tapering portion including lateral ball seatings in the wall of the housing of substantially constant circumferentialthickness and a metal ball mounted therein, the method of increasing the clearance between the writing ball and its seatings in the housing which consists in forcing a tool onto the tapering portion of the exterior of the nib, which tool has a bore the peripheral edge of which is chamfered, such that the chamfered end of the bore contacts and applies a constricting force exceeding the elastic limit of the nib structure to a zone in the form of a circular band which extends circumferentially of the tapering portion of the nib exterior to assure a permanent deformation of the nib, which zone is located parallel to and to the rear of the plane tangential to the rear of the ball and perpendicular to the axis of the nib and no greater than three ball diameters radially distant from the center of the writing ball, such that the said clearance -is increased.

4. In the manufacture of a ballpointed writing instrument having a nib comprising a metal ball-accommodating housing including radial ball seatings in the wall of the housing of substantially constant circumferential thickness, and a metal ball mounted therein, the method of increasing the clearance between the writing ball and its seatings in the housing, which housing is composed of a metal having a low elastic limit, which includes the step of subjecting the exterior of the nib to a constricting force exceeding the elastic limit of the nib structure at a zone which extends circumferentially of the nib exterior to assure a permanent deformation of the nib, which zone is located parallel to, and to the rear of, the plane tangential to the rear of the ball and perpendicular to the axis of the nib and no greater than three ball diameters radially distant from the center of the writing ball, the axial distance between the said zone and the said plane being such as to provide the desired increase of clearance between the writing ball and its seatings in the housing.

5. In the manufacture of a ballpointed writing instrument comprising a nib having a metal ball-accommodating housing including radial ball seatings in the wall of the housing of substantially constant circumferential thickness, and a metal ball mounted therein, the method of increasing the clearance between the writing ball and its seatings in the housing, which includes the step of applying to the exterior of the nib, which nib is composed of metal, a constricting force exceeding the elastic limit of the nib structure acting simultaneously on the whole of the circumference of the nib exterior around a zone located to the rear of, and adjacent and parallel to, the plane tangential to the rear of the ball and perpendicular to the axis of the nib andno greater than three hall diameters radially distant from the center of the writing ball, to assure a permanent deformation of the nib whereby the said clearance is increased.

References Cited in the tile of this patent UNITED STATES PATENTS 

